Solubility of Aluminum Sulfate in Near-Critical and Supercritical Water

Abstract

The solubility of aluminum sulfate in sub- and supercritical water (SCW) has been measured using a flow system at temperatures and pressures ranging between (619 and 675) K and (15 and 29.2) MPa, respectively. Experimental solubility values (in terms of mole fraction) varied from 1.61·10–5 to 2.94·10–5 under the conditions studied in this work. These data have been fitted by response surface methodology (RSM) obtaining values for an average percentage deviation (APD) of 6.2 %. To extend temperature and pressure ranges analyzed, a theoretical solubility model based on the Flory–Huggins approach was applied, leading to worse predictions than the previous model. Subsequently, some additional empirical and semiempirical approaches were also used for the description of the solubility. As a result, a very simple approach (a polynomial function of fluid density) reached an accuracy even better (APD = 5.8 %) than the more complex polynomial model derived from response surface methodology.